Open-source SCSI targets

Mainstream

The two main open-source multiprotocol SCSI targets in the industry are:

LIO (Linux-IO) is the standard open-source SCSI target in Linux by Datera, Inc. It went upstream with Linux kernel version 2.6.38.[1][2][3]

COMSTAR (Common Multiprotocol SCSI Target) is a software framework that enables any SunOpenSolaris host to serve as a SCSI target that can be accessed over the network.

Linux out-of-tree and legacy

In Linux, there are also three out-of-tree or legacy SCSI targets:

IET (iSCSI Enterprise Target) is an iSCSI only target that is now unsupported. Its aim was to develop an open source iSCSI target with professional features that works well in enterprise environment under real workload, and is scalable and versatile enough to meet the challenge of future storage needs and developments. This target was quite popular, but its user base has been deteriorating, because of its lack of support and modern features.

SCST (SCSI Target Subsystem) is a generic SCSI target engine for Linux that has been developed by a team in Russia. Its iSCSI implementation is an improved version of IET. SCST has made Linux usable as a SAN operating system, but lost momentum and was acquired by Fusion-IO in March 2013.

STGT (SCSI Target Framework) has been the standard multiprotocol SCSI target in Linux. It aimed to simplify SCSI target driver creation and maintenance. Its key goals were the clean integration into the scsi-mid layer and implementing a great portion of the target in user space. STGT was superseded by LIO with Linux kernel 2.6.38.[1][2][3]